Length measurement using optical signals can be performed using two general methodologies. The first approach uses the incoherent detection of light pulses to determine time-of-flight information, which is then converted to distance. While this approach is suitable for long distance measurements, high-precision measurements are generally unavailable due to hardware performance limitations. The second methodology uses detection of optical coherence, also referred to as interference fringes, to perform length or distance measurements with high precision. This technique is suitable for the precise measurement of incremental or relative displacements. However, it is not suitable for measurement over large distances where an absolute measurement is required. In an effort to overcome the aforementioned limitations, methods have been developed that use a separate fast detector to determine time of flight and an optical spectral analyzer to perform fringe-resolved cross-correlation to increase the measurement precision. These methods, however, are complex and require significant hardware resources. Thus, a need exists in the industry to address the aforementioned deficiencies and inadequacies.